I will attempt to elucidate the mechanisms by which yeast switch their developmental program from mitosis to meiosis. I will study the macromolecular synthetic events leading from the diploid cell to the ascus containing four haploid ascospores, and how inhibitors of protein or RNA synthesis affect these events. Conditional mutants unable to sporulate at 30 degrees but normal at 23 degrees will be sought in a strain homozygous for a temperature sensitive suppressor. Changes in the chromatographic profile of DNA dependent RNA polymerase will be investigated to see whether they relate to transcriptional control of spore-specific gene products. The isoaccepting species of transfer RNA will be screened to see whether there are changes during sporulation related to translational controls.